This invention relates to the automatic dispensing of non-round, flexible, elastic containers from nested stacks of such containers, and particularly to the dispensing of pressed or drawn, flanged paperboard containers having a water- or grease-resistant coating (for example, polyethylene or polyester) on the inner wall of the container.
Such containers are being used increasingly instead of metal foil containers in the food processing industry for a wide range of products, such as, pies and other bakery items. One advantage of paperboard containers is that they can be used in microwave ovens, whereas metal foil containers should not.
In many commercial food processing applications containers must be automatically dispensed one at a time at speeds of up to 150 containers per minute from the bottom of a nested stack of such containers and deposited onto holders on a traveling conveyor. The conveyor carries the containers through the other operations in the food processing sequence, including filling the empty containers with food. It is apparent that a reliable and accurate method must be used for automatically dispensing the containers one at a time and for depositing them on the carriers.
The usual apparatus for dispensing metal foil containers in continuous food processing machinery employs continuously rotating cooperating screws or rotors that separate and strip the bottommost plate from the vertical nested container stack while supporting the penultimate plate and the remainder of the stack. The screws or rotors typically comprise flat, annular plates having stepped flanges and channels to separate and dispense the bottommost plate in the stack.
These conventional screw-type machines for metal foil plates and containers, however, cannot be used without modification for pressed or drawn paperboard containers because of structural differences between metal and paperboard containers. Among these differences is a bead on the outer perimeter of the flange of the metal container. When beaded metal containers are nested, the beads create a space or cleavage between the adjacent flanges. A separator blade carried, for example, by the rotor of a screw-type dispensing machine can be easily inserted into the cleavage between the flanges of the bottommost and penultimate containers to separate the bottommost container from and to support the remainder of the stack. However, it is not feasible to provide beaded flanges on the pressed paperboard containers of the type used with the present invention.
Another structural difference is that paperboard containers are generally heavier than metal foil containers. This makes it more difficult to insert a separator blade between the flanges of paperboard containers as compared to metal containers, for the following reason. When the nested stack of paperboard containers is supported for dispensing on the rotors of a screw-type dispensing apparatus, the flange of the bottommost container is supported by the rotors. That flange is bent upward at the points of support due to the weight of the stack bearing down on the support points, causing the flange of the bottommost container to touch the flange of the penultimate container. Accordingly, there is no space between the flanges of the bottommost and penultimate containers into which a separator blade can be inserted.
A third difference is that aluminum and other metal containers can be manufactured to more exact tolerances than pressed or drawn paperboard containers. Thus, paperboard containers exhibit wider variations in flange size and other dimensions, making them more difficult than metal containers to dispense from a stack.
The art has attempted to overcome these problems associated with the use of paperboard containers principally by resorting to the use of vacuum-type dispensers. In one variation, the vacuum pick and slide method, a suction source carried by a movable arm contacts the bottommost plate on the stack. Movement of the arm separates (or "picks") the bottommost container from the stack. The plate is then deposited at the top of an inclined ramp on which the plate slides down onto the carrier. In another variation, the vacuum pick and place method, the bottommost plate is picked from the stack by a suction source carried by a movable arm and placed directly onto the carrier by the moving arm. These vacuum methods are slower, less reliable, and less economical than the dispenser of the present invention.